You can extract the Red, Green and Blue components from color grayData

by using
red(grayData)
green(grayData)
blue(grayData)

Then the red, green and blue data will return the same values...
so you can use either of them.

Thank you very much for answering,
but it dos not work right now


For a better understanding i should send you the whole code:

---

import processing.video.*;
import processing.serial.*;

Capture cam;

Serial myPort;  // Create object from Serial class


void setup() {
 
 size(200, 160);
 myPort = new Serial(this, Serial.list()[0], 115200, 'N', 8, 2.0);
 String[] devices = Capture.list();
 println(devices);
 cam = new Capture(this, 10, 8, devices[2]);
 
}


void draw() {
 rect(20,20,20,20); //rect(x, y, width, height)
 noFill();
 stroke(255);
 frameRate(5);
 
 if (cam.available() == true) {
   cam.read();
   cam.filter(GRAY);
   image(cam,0,0,200,160); //image(img, x, y, width, height)
   rect(21,21,2,2); //rect(x, y, width, height)
   noFill();
   stroke(255);
 }
 
 cam.loadPixels();
 color grayData = get(22,22) ; // den pixel aus dem quadrat von rect...
 int greyLevel = grayData & 0xFF;

 println ("  binary = "+binary(grayData)+"  hex = "+hex(grayData,6)+ "  byte = "+byte(grayData));  // als Beispiel : 11111111 01011101 01011101 01011101



things that can help. i got it from other kind discussions
//  byte b1 = (byte)(ceil(grayData) & 0xFF);
//  byte b2 = (byte)( (ceil(grayData) >>> 8) & 0xFF );
//  println (b1 +"  "+b2);


//  float grayDataToSend = ceil( map (grayData, 0, 255, 735, 2520));
 
   myPort.write(0xAA);
   myPort.write(0xA0);
   myPort.write(0x55);
   myPort.write(0x04);
   myPort.write(1);
   myPort.write(1);
   myPort.write(25);
   
   myPort.write(0xAA);
   myPort.write(0xA0);
   myPort.write(0x55);
   myPort.write(0x03);
   myPort.write(1);
   myPort.write(1);
   myPort.write(0);
   
   myPort.write(0xAA);
   myPort.write(0xA0);
   myPort.write(0x55);
   myPort.write(0x01);
   myPort.write(0x01);
   myPort.write(0x02);
   myPort.write(0xDC);  //here must be the low byte
   myPort.write(0x02); //and here the high byte of servoposition
}

---

The reason for that, asking your self
I would like to control a position of a simple servo motor (from max to max angle position) by brightness values of a web cam (one pixel from white to black). It shall be a nice installation with interact moving parts.

For this i use a iMac and a SD84 USB controller (http://www.robot-electronics.co.uk/htm/sd84tech.htm.

The problem is....i am a noob in Processing

Hey, it looks like you've essentially used what I suggested, though I note now that the description was incorrect; "masking" by bitwise-and-ing with 0xFF gets you the blue bits, not the red bits (hopefully, if the cam colour value is actually grey, there will be no difference).

zoodo wrote on Dec 21^st, 2009, 4:57am: